Method of changing frequency of alternating currents.



No. 682,943. Patented Sept. l7, mm. B. G. LAIIE.

IETNOD 0F CHANGING FREQUENCY OF ALTERNATIIG CURRENTS. (Application am an 94, 1097 (lo Iodul.)

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I UNITED STATES PATENT OFFICE.

BENJAMIN G. LAMME, OF PITTSBURG, PENNSYLVANIA, ASSIGNOR TO THE VESTINGHOUSE ELECTRIC AND MANUFAOTURIN G COMPANY, OF PENN- SYLVANIA.

' METHOD OF CHANGING FREQUENCY OF ALTERNATING CURRENTS.

PECIFIGATIOKfoming part of ma Patent are. 682,943, dated September 17, 1901. Application filed July 24. 1897. Serial No. 645,797. on specimens.)

To all whom it may concern:

Be it known that I, BENJAMIN G. LAMME, a citizen of the United States, residing in Pittsburg, in the county of Allegheny and State of Pennsylvania, have invented anew and use- 4 ful Improvement in Methods of Changing the Frequency of Alternating Ourren ts, (Case No. 750,)015 which the following is a specification. r0 Myinventionrelates to alternating-current transformation; and it has for its object to provide a method of changing the frequency of alternating currents which shall be reliable and effective and which shall have a is wide range of usefulness.

r In the accompanyingdrawin'gs, Figurel isa diagrammatic view of a machine for securing alternating currents of different frequencies, and Fig. 2 is a similar view of a modified form of machine. Fig. 3 is a sectional view of the laminated core of the machine shown in Fig. 1.

Referring particularly to Figs. 1 and 3, 1 is a laminated ring-core which is nnprovided 'with magnetizing-coils and serves merely as a keeper or a return-path for the lines of force and maybe mounted in asuitable supporting-frame 2 This ring 1 is provided with notches 3, the number and location of such notches depending upon the number of phases of current which it is desired to secure from the machine. The employment of such notches is necessary inorder to avoid local magnetic fluxes at the points where the brushes are located. While no specific form of notches is essential, proper commutation cannotbe effected without the employment of notches of some form at the points where the commutator-brushes are located.

4 is the winding of the armature of the machine, which is here indicatcd diagrammatically for convenience of illustration as of ring form; but in practice it. would probably.

be of the more usual drum type. This winding is connected to exit-able collector-rings 5 and also to a commutator-cylinder 5", on which bear brushes, the number of which corresponds to the number of phases of current. The brushes 4; and 8 being diametrically 5e opposite each ether and corresponding to one phase are electrically connected to each other and to the lead 10, and in the same manner and for the same'reason the brushes 7 and 9 are connected together and to-the lead 11. Two currents differingin phase are supplied to the winding of the armature 4 by means of the collecting-rings 5 and brushes 12 through the leads 13. If the armature 4 be rotated at a synchronous speed, the alternating armature-current will generate a field 6o fixed in space, the field-ring 1, as has already been stated, servingqn vas a keeper or return-path for the lll'lel. uL i'orce. \Vhen thus rotated at, a synchronous speed, the brushes 6 Sand 7 J will take off a direct current and supply the same to the leads 10 11. If the armature be run ataspeed slightly below synchronism. the brushes will take off an alternating current having a frequency represented by the drop in speed below syn- 7o chronism. A'fnrther drop in speed will increase the frequency of the alternations delivered from the brushes to the circuit 10 11 until the armature is brought to rest, when the alternations will be equal to those supplied by the leads 13 the brushes 12, and rings 5 to the armature 4. Referring now to Fig. 2 of the drawings, the armature 4, collecting-rings 5, commutator-cylinder 5, and alternating-current loads 13 are the same as those shown in Fig. 1 and above described. The laminated ring or keeper 1 is also the same, except that it has eight notches 3 instead of the four notches 3 of Fig. 1. There being a commutator-brush correspondiu g to each notch 3 and those diametrically opposite each other being electrically connected for one phase, it will be seen that the brushes 14', which have been added between those shown in Fig. 1, will deliver alternating currents one-half an alternation behind or ahead, as the case may be, those of the other circuit. By rotating the armature at different speeds, as has already been described in connection with Fig. 1, two-phase 5 alternating currents will be delivered. which,

as regards the rate of alternations, dilfer in any desired degree from the currents supplied to the machine. It-will also be understood that the notches and corresponding brushes may be varied in number and position from those shown to secure a different number of phases of current, if desired.

In order that the operation of the apparatus in the manner described may be satisfactory, the core or keeper should be laminated and should have either the same number of notches as there,are poles in the rotating field produced by the polyphase currents supplied to the winding of the rotating member of the machin$dramultip1e of that number, according to the number of, phases of current taken from the commutator.

' It is probable that the apparatus might be operated without the notched ring or keeper 1on1; but in such case the alternating magietiz'ing-current would be very large unless amper'e' -turns.

sparking at the commutator, whereas with the a'rmature had a very great number of This would lead to serious with magnetizing-coils and running said ar mature at such speed between zero and synchronism as will insure the supply of currents of the desired frequency to the commutator: leads. I

2. The method of producing alternating currents of any desired frequency which consists in supplying alternating currents of a given frequency to the armature-winding of a rotary transformer having no magnetizing field-coils, and driving the armature at such speed between zero and synchronism as will provide a current of the desired frequency at the commutator-brushes.

3. The method of changing the frequency of alternating currents which consists in su'p plying alternating currents of a given frequency to the winding of the rotatable member of an electrical machine through brushes and collector-rings, rotating said member in proximity to a magnetic keeper at a speed corresponding to the desired current frequency and taking off the transformed current through a commutator.

In testimony whereof I have hereunto sub scribed my name this 22d day 0f-July, A. D. 1897.

BENJ. G. LAMME.

Witnesses:

WESLEY G. CARR, H. C. TENER. 

